In the construction of wooden frame buildings it is common to set evenly spaced floor joists, typically formed from nominally dimensioned 2.times.8-2.times.12 ("two-by-eight to two-by-twelve") lumber on foundations or wall headers to define a floor surface. These lumber pieces are laid in parallel, spaced typically at a sixteen-inch on-center spacing. The lumber pieces in such an arrangement are known as joists. They are set so as to span a floor or ceiling space with the nominal two-inch (e.g. "two-by") dimension extending in a horizontal (widthwise) direction and the nominal eight to twelve inch (e.g. "eight-by to twelve-by") extending in a vertical (heightwise) direction. In this manner, the joists each define a load-bearing beam for supporting a portion of the weight of the floor/ceiling. Over the joists are typically placed sheets of wafer board, plywood, solid planks, or another suitable natural or man-made subfloor material. Over the layers of subflooring can be placed finish flooring such as tile, carpeting or hardwood strips. The subfloor is secured to the joists against the "two-by" dimension face of the joists using nails, screws and/or adhesives. The subfloor pieces are often joined together at tongue and groove edge details that interlock with each other to define a fairly even, level and smooth subfloor surface.
It is highly desirable to maintain a stable joist-to-joist spacing along the entire span length. It is further desirable to maintain the parallelism of the joists along the vertical direction. In this manner, the placing of subfloor pieces is more predictable and accurate. It is further desirable to maintain the parallelism and spacing between joists so that the floor does not subsequently move, acquire dead spots.
One common problem encountered with floors, subsequent to installation, is that the joists become non-parallel. For example, the ends of the joists that are opposite to the subfloor (in the vertical direction) can become splayed through curling or warping of the wood. This can cause torsion and detachment of joists from the subfloor. This results in dead spots, and waves that show up in the finished floor.
The tried and true technique for preventing curling, and for ensuring evenly-spaced, parallel joists is to install solid blocking between each pair of adjacent joists along the center of the span and, possibly, at other portions of the span. These blocking pieces are, in essence, sections of joists that have been cut to the appropriate joist spacing (16 inch or other on-center spacing) and that run the full vertical width of each joists. Typically these blocks extend transversely to the span direction of the joists and are secured by through-nailing each of the joists to pin opposing ends of the blocking into place. Blocking pieces are staggered by a few inches along successive adjacent joists to provide space to through-nail each blocking piece. A disadvantage of blocking is that it is time consuming to install. Each piece must be individually measured, cut, placed and nailed at several points along the vertical height of the joist. Wherever a blocking piece is installed, holes must be cut to allow mechanical systems such as wires and pipes to pass therethrough. Such holes may weaken the structural integrity of the blocking piece, and are time consuming to cut.
An alternate technique for attempting to secure joists together involves the use of crossed pieces of wood each cut on an angle. The crossed wood members, known generally as "bridging," may be formed from solid wood pieces or composites such as plywood and waferboard. A bridging structure according to the prior art is detailed in FIG. 1. Pieces of bridging 20 are placed together at appropriate locations along the span between each of two joists 22 to form an X-shaped bridging structure. The pieces 20 are located between joists 22 beneath the subfloor 23. Nails 24 are driven through the bridging pieces 20 so that they pass into the adjacent joists, thus securing the pieces in place. These bridging pieces 20 are often cut en masse to a single uniform length. A uniform cut length can be used since slight variations spacing between joists are accommodated by slightly increasing or decreasing the acute intersection angle (A) of the "X." The completed X-shaped bridging structures have an advantage over blocking in that they more freely allow mechanical to pass therethrough. However, they are notoriously weak and tend to pull apart over time. See, for example, the arrows 30 which show the pulling apart of bridging pieces 20 as joists 22 curl (arrows 32). The bridging offers little resistance to such curling.
It is, therefore, an object of this invention to provide a joist-securing spacer clip, and associated method for securing joists together with such spacer clips, that maintains the parallelism and spacing between joists along their span. A spacer clip of this type should be easy and inexpensive to produce, universally applicable to a variety of sizes and layouts of joist work and should allow the relatively free passage of mechanical system components (pipes, conduits, etc.) therethrough. A method for installing such spacers should be straight forward and relatively quickly for workers of average skill in the construction art, and should employ a minimum of external fasteners.